Air conditioning process

ABSTRACT

A process for efficiently conditioning air for beneficial use by sequentially cooling dry air in three distinct steps, e.g. precooling the air out of the presence of moisture, refrigerating the air to cool the air and coincidentally condense excess moisture, and adiabatically cooling the air in the presence of moisture.

United :States Patent 1 1 [111 3,890,797 Brown I 24, 1,75

[54] AIR CONDITIONING PROCESS 2,811,223 10/ Newton 62/92 inventor: e R.r 2 i c m v 3,247,679 4/ 966 Mecklen, 62/91 Ave, Salt Lake City, Utah84105 [22] Filed: Nov. 23, 1973 Primary Exarr'z'inefl-William .l. Wye

. Attorney, Agent, or Firm--H. Ross Workman; J. I21] App]. No.. 418,527Winslow Young Related U.S. Application Data [60] Division of Ser. No.359,368, May ll 1973, which is u continuation-in-part of Ser, No,172,968, Aug. 19, 1971 abandoned. ABSTRACT [52] U.S. Cl. 62/91; 62/93;62/3l 1;. A process for efficiently conditioning air for beneficial62/92 use by sequentially cooling dry air in three distinct [51] Int.Cl. F25D 17/06 steps, e.g, pre-cooling the air out of the presence of[58] Field of Search 62/91, 93, 31 1, 92 moisture, refrigerating the airto cool the air and coincidentally condense excess moisture, andadiabatically [56] References Cited cooling the air in the presence ofmoisture.

UNITED STATES PATENTS 1,863,576 6/1932 Morse 62/271 2 Claims,-1 DrawingFigure WARM AIR (dry) WATER R HEAT E EXCHANGER V RY COLD AIR WASHEREVAPORATING l COOL COLD couosrvssn COMPRESSOR AIR CONDITIONING PROCESSBACKGROUND' 1. Field of the Invention I A tion Ser. No. 359,368, filedMay I l, l973. which is in turn continuation-in-part of my copendingapplication Ser'. No. 172,968. filed Aug. 19, 1971 (now abandoned). Thepresent invention relates to the production of low temperature gasessuch as air for beneficial use in air Conditioning.

2. The Prior Art' It is well-known that the efficiencyof airconditioning systems is highly dependent upon the temperature of ambientair. ln summer months. where the ambient air temperature is high,usually refrigerated air conditioning systems are employed to produceconsistently cold air. This is particularly true where-high temperaturesare accompanied by relatively high humidity levels. Socalled ,swampcooler .type airv conditioning systems become of almost negligible valuewhen both the temperature'and humidity of ambient air are high.

Because of the great difficulty with which air is reduced to a very lowtemperature in hot summer months, most air conditioning systems havebeen engineered so as to recirculate and recool the conditionedairinstead of continuously cooling fresh air. This procedure has beenfound necessary to keep the size and attendant costs of air conditioningsystems from becoming proh'ibitiv e. Until this present invention, aneconomical and efficient way of substantiallyreducing the temperature ofair or other gas for cooling purposes year-round withoutrefrigerationihas not been known.

It is also well-known to condition air b y' successive cooling.humidifying, drying and recooling steps which are inefficient,complicated and expensive. See, for example. U.S. Pat. No. 1,863,578

BRIEF SUMMARY AND OBJECTS OF THE IN E TIO I The present invention.relates to conditioning fresh air by sequentially (1) pre-cooling dryair outof the presence ofmoisture. (2) refrigerating to cool the air andcoincidentally condense excess moisture and (3) adiabatic-allycooling-the air. Surprising efficiency and cooling results from thisprocess using a total fresh air system and treatment of the air inquantities between 400 and 600 cubic feet per minute per ton of netsensible in-space cooling.

It is, therefore. a primary object to efficiently provide air havingcontrolled temperature and humidity for air conditioning i l i It isanotherimportant object to provide a process for effecting sensiblecooling usinga total fresh air system.

These and other objects. and features of the present invention willbecome more fully apparent from the following description and appendedclaims taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a schematic flow diagramillustrating a fluid circuit and apparatus for reducing air temperatureaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT GENERAL Heat exchangeprocesses suchas used in air condi-' of the gas is high. the difficultywith which heat is removed increases at an astonishing rate when the temperature ,of the gas is already low. Thus, generally speaking,it is mucheasier and less expensive to make hot air cool than to make cool aircold using prior art techniques. Historically, the approach used to makecool air cold was to increase thesize and capacity of cooling systems. ir

The presentinvention includes treating dry warm air out of the presenceof moisture to reduce its wet bulb temperature. Air most efficientlyused with.the illustrated embodiment has a dew point of not more than 57which is low compared to the dry bulbtemperature of the warm air, Thistreatment can be performedby pre-cooling in a conventional heatexchanger. I According to the present invention. the temperature of thepre-cooled gas is first reduced by refrigeration which serves to furtherremove moisture and finally is adiabatically reduced so that the gas iscold. Adiabat ic processes are defined asthose processes carried out insuch a manner thatheat is not exchanged between the system,and itssurroundings. Thus, the adiabatic cooling stepdoes notrequire an energyinputto reduce the temperature. When the gas is adiabatically cooled HO.cording to the present invention, heat is not actually removed fromthe-cooling system but is reducedpsychrometrically. I v w. 'If astreamof gas is intimately mixeduwith a quantity of recirculating liquidat a given temperature in an. adiabatic system,-'the temperature of the.gas will drop and its humidity will increase. Furthermore; the.tempera-. ture of the recirculating liquid will approach the web bulbtemperature'of the gas. I When 100 percent fresh (unrecirculated) airisIused for cooling, air quantities treated according to the preferredembodiment of the 'inventionmustnecessarily be'li mited to a rathernarrow range. in-order to efficiently produce desired cooling to withina range of-53.? to 60F without imposing larger than-necessary-precoolingand refrigeration loads on the air cooling process.

It has been found according'to the present invention that approximately400 to 600 cubic feet of fresh air per' minute per ton (CFM/ton) of netsensible in-space cooling isan adequate amount to develop conditionedair at a desirable temperature of between 53 and 60F. The'surprisingefficiency of this syste'm can'be recognized by observing thatconventional fresh air swamp coolers require about I000 CFM/ton even"with very dry fresh air. The efficiency of the system using this airvolume range presumes I00 percent fresh (unrecirculated) air having adew point of not more than 57F coincident with dry bulb temperatures ofnot less than F. Under these climatic conditions. the presentlypreferred embodiment of the invention produces 53 to 60F moistureconditioned air with surprising effi- 3 ciency and withoutrequiringintermediate drying steps. In this specification, refrigerationis defined to include cooling with mechanically or chemicallyrefrigerated fluids.

Referring more particularly to the FIGURE. warm dry air is firstobtained from a fresh air source. eg ambient. To maximize the efficiencyof the system. the dew point of the air should be at least as low as 57Fwhen air having a dry bulb temperature of not less than 90F is used.

The warm air is first pre-cooled in a heat exchanger 62. The heatexchanger 62 may be any one of a variety of heat exchangers which willnot add moisture to the air, one suitable type being the fin-coil heatexchanger often called an extended surface heat exchanger. This type ofheat exchanger is very inexpensive to acquire and operate and is veryefficient at high temperatures.

Therefore, according to the illustrated embodiment of the invention, thepre-cooled dry air emerging from the heat exchanger 62'is conducted to arefrigeration coil 76 which acts upon the pre-cooled air as it traversesfrom the heat exchanger 62 to the air washer 64 (i.e. from thepre-cooling to the adiabatically cooling steps). When the pre-cooled airis further cooled, its wet bulb temperature is lowered. Accordingly,upon adiabatic cooling in the air washer 64, its dry bulb temperature isfurther reduced to about 53 to 60F.

The moisture content of the effluent from the air washer 64 will becontrolled in proportion to the amount of cooling to which the air issubjected in advance of the adiabatic cooling in air washer 64. The drybulb and wet bulb temperatures imposed upon the air in advance of theadiabatic cooling step will determine the amount of moisture that can beadded in the adiabaticcooling step.

The air is then directed through air washer 64 which scrubs the air withwater or. if desired. other cooling liquid. The water used to scrub thepre-cooled dry air is recirculated through an external circuit 66continuously. The temperature of the recirculating water in the circuit66 approaches the wet bulb temperature of the air which enters the airwasher 64. Thus, the entering cold air has its temperature furtheradiabatically re duced from the dry bulb to near the web bulbtemperature in the air washer.

The refrigeration circuit 70 conventionally comprises a condenser 72 anda compressor 74 with an evaporating coil 76 interposed therebetween. Aconventional expansion valve 78 admits refrigerant fluid into theevaporating coil 76.

it should be observed that unless the temperature of the air wereadiabatically reduced in the air washer 64, a far larger and moreexpensive coil 76 and larger refrigeration system 70 would be necessaryto obtain the same very cold air temperature developed according to theembodiment of the FIGURE.

The system of the FIGURE is designed to transport and condition about400 to 600 CFM/ton net sensible cooling. Using the air having a 57 dewpoint. temperatures as low as 53 to 60F may be economically andefficicntly achieved. Accordingly. the effluent conditioned air has asurprisingly low temperature and controlled humidity without requiringexpensive dehumidifying (warming) and recooling steps.

Using the embodiment of the FIGURE. cold air in the range of 53 to 60Ffor air conditioning or any other desired beneficial use can be obtainedwith surprising efficiency using a 100 percent fresh air system atmaximum outdoor temperatures. Thus. the need for recirculating the sameair in order to reduce the costs of cooling is unnecessary. Furthermore,cold air can be obtained without using large and expensive refrigerationsystems. The refrigeration system required for this combination ofcooling steps has been found to be approximately one-third the sizerequired if conventional recirculating air refrigeration systems areemployed. Accordingly, the advantages of a complete fresh air system canbe substituted for the lower quality. more expensive recirculating airsystems.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described embodimentis to be considered in all respects only as illustrative and notrestrictive and the scope of the invention is, therefore. in: dicated bythe appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed and desired to be secured by United States LettersPatent is:

l. A process for controlling the temperature and moisture content of airhaving a dew point of not more than 57F corresponding to at least F drybulb temperature. sequentially preparing an air flow path accommodating400-600 CFM/ton net sensible cooling; drawing fresh dry air exclusivelyfrom a fresh air source and through the flow path in the amounts of 400to 600 CFM/ton net sensible cooling; pre-cooling the fresh. air with aheat exchanger without altering its moisture content; refrigerating thepre-cooled air to further cool the air and coincidentally condenseexcess moisture; and

scrubbing the cooled air with recirculating water to adiabatically coolthe air to within a range of 53 to 60F.

2. A process for conditioning air sequentially comprising (a) firstcooling percent fresh air having a dew point of not more than 57Fcorresponding to at least 90F dry bulb temperature without altering itsmoisture content; (b) second cooling the air by refrigeration to reducethe wet bulb and dry bulb temperature and to control the amount ofmoisture which can be added; (c) third cooling the air adiabatically towithin the range of 53 to 60F by scrubbing the air with recirculatingwater; all three cool ing steps being applied sequentially to airquantities exclusively within the range of 400 to 600 CFM/ton netsensible cooling.

1. A process for controlling the temperature and moisture content of airhaving a dew point of not more than 57*F corresponding to at least 90*Fdry bulb temperature, sequentially preparing an air flow pathaccommodating 400-600 CFM/ton net sensible cooling; drawing fresh dryair exclusively from a fresh air source and through the flow path in theamounts of 400 to 600 CFM/ton net sensible cooling; pre-cooling thefresh air with a heat exchanger without altering its moisture content;refrigerating the pre-cooled air to further cool the air andcoincidentally condense excess moisture; and scrubbing the cooled airwith recirculating water to adiabatically cool the air to within a rangeof 53* to 60*F.
 2. A process for conditioning air sequentiallycomprising (a) first cooling 100 percent fresh air having a dew point ofnot more than 57*F corresponding to at least 90*F dry bulb temperaturewithout altering its moisture content; (b) second cooling the air byrefrigeration to reduce the wet bulb and dry bulb temperature and tocontrol the amount of moisture which can be added; (c) third cooling theair adiabatically to within the range of 53* to 60*F by scrubbing theair with recirculating water; all three cooling steps being appliedsequentially to air quantities exclusively within the range of 400 to600 CFM/ton net sensible cooling.